Lime and silica-rich high alumina cement,and process for manufacturing same

ABSTRACT

A LIME AND SILICA-RICH HIGH-ALUMINA CEMENT AND THE PROCESS FOR MANUFACTURING IT. A LIME AND SILICA-RICH HIGH ALUMINA CEMENT WHICH CONSISTS, IN PARTS BY WEIGHT, OF ABOUT: 8 TO 10% SIO2 ABOUT 1 TO 2% TIO2 26 TO 29% AL2O3 14 TO 16% FE2O3 O% OR TRACES FEO 45 TO 48% CAO THE MODULI: SIO2/AL2O+FE2O3 BEING IN THE RANGE OF ABOUT 0.18 TO 0.25 AL2O3/CAO FROM 0.55 TO 0.65 AL2O3/SIO2 BETWEEN ABOUT 2.6 AND 3.6 AND THE MINERALOGICAL COMPOSITION CONTAINING CA, C2S, C12A7 AND FERRITES. THE CEMENT HAS A BROADER RANGER OF USE AND ITS PREPARATION IS CHEAPER.

AU 112' EX US. Cl. 106104 3 Claims ABSTRACT OF THE DISCLOSURE A lime and silica-rich high-alumina cement and the process for manufacturing it.

A lime and silica-rich high alumina cement which consists, in parts by weight, of about:

8 to 10% so, about 1 to 2% TiO; 26 to A1203 14 to 16% 1%,0, or traces FeO 45 to 48% CaO the moduli:

SiO /Al O +Fe O being in the range of about 0.18 to 0.25 Al O /CaO from 0.55 to 0.65 Al O /SiO between about 2.6 and 3.6 and the mineralogical composition containing CA, C S, C A and ferrites.

The cement has a broader range of use and its preparation is cheaper.

The present invention relates to a new lime and silicarich high-alumina cement; another object is a process for manufacturing said cement. It should be precized that alumina cements are often named ciment fondu (i.e. fused cement).

Numerous alumina cements are already known which, in practice, have satisfactory refractory and mechanical qualities (see Robson: High Alumina Cement and Concrete-ed. Wiley and Son, 1962), but research is constantly going on to improve these cements, and more particularly to obtain cements having equal, or at least, equivalent, qualities at lower cost. With this end in view, it was possible to study compounds which do not possess hydraulic properties and try to render them reactive by physical or chemical treatments; efforts have been made, for instance, to ativate gehlenite in various manners. It was also possible to try to use various known compounds which were unusable on account of their being too reactive, by changing their behavior to eliminate their harmful properties; in this connection QA and cmAq, the presence of which in alumina cements is very often considered as undesirable, may be mentioned.

In the present specification A represents A1 0 S represents SiO, and C represents CaO.

Applicants have chosen to undertake work on altering the behaviour of the aforesaid known compounds. A first series of studies on the preparaiton, with or without additives, of a lime (CaO)-rich high-alumina cement, showed that the resistances and strengths obtained with a binder prepared from a bauxite crude comprising less than 5% SiO-, (45%) and limestone (55%) were markedly lower than those of normal high-alumina cement, but not very reactive at the aging temperature.

3,705,815 C Patented Dec. 12, 1972 Applicants then considered using a SiO -rich bauxite, usually rejected for the industrial manufacture of highalumina cements, to prepare lime-rich high alumina cements; if this solution were proved possible in practice it would, in fact, have the advantage of permitting poor quality bauxite to be used (notably certain French bauxites), and consequently provide a savingof approxi mately 30% in the cost of the cement in question, compared with present day high-alumina cement.

To manufacture a hydraulic binder which can be used either in building or to agglomerate iron. powders to be treated in a blast-furnace, it has further already been suggested to employ bauxites having an Al O :SiO ratio smaller than 1.5, and which cannot be used for cement manufacture, the silicate (SiO :Al O +Fe O modulus being less than 5; according to this known process, said crude is then ground, sintered in a rotary furnace at temperatures not exceeding 1300 C., and finally has from 1 to 5% calcium carbonate added there- 0.

During their work and research, applicants established that the binder so obtained had average mechanical qualities and did not possess refractory properties, and further the unexpected fact that it was possible to obtain a high-alumina cement having, at the same time, refractory characteristics substantially equal to those of conventional high-alumina cements, by using a crude consisting of poor quality bauxite and lime. The cement according to the invention is characterized in that it consists, in parts by weight, of about:

8 to 10% of SiO,

0% or traces FeO 45 to 48% C210 l the moduli 510, 15. 20 A1 0, 43.00 PC5303 T102 2.35 'CaO 0.90

Water plus MV 13.85

50 to limestone (such as Orgon limestone).

Generally speaking the setting time of high-alumina cement can be controlled at will by varying the CaO content. Between 0 and 4 hours, for instance, for the start of setting. In the following case the setting time lasts from 2 hours 10 minutes (start) to 2 hours 40 minutes (end) its bending strength (in micro-concrete W/C=0.40, aging 20) is, in bars, about 23 at 4 hours 39 at 6 hours 71 at 1 day 81 at 7 days .MgO traces, with the ratio A:C from about 0.55 to and its compression strength (in micro-concrete W/C= 0.40 aging 20) is, in bars, approximately 120 at 4 hours 255 at 6 hours 555 at 1 day 765 at 7 days The mixture was fused at between 1450 and 1500 C., then run out and cooled in 60 minutes from 1450 to 800 and in 60 minutes from 800 to 22 C.

The product obtained was then crushed to a Blaine specific surface of 3040 cm. g.

It was found that when the process of the invention was carried out, the cooling rate and nature of the oxidizing A process for obtaining high-alumina cement according atmosphere had a y marked effect On i116 mint/1:81 to the invention is characterized in that a silica-rich 8 composlflon of dlnkers and Coolmg bauxite d a limestone are i d by crushing so as to 10 rate substantially afiecttng the. concentration ofphases and form a crude having the following composition calculated f q y the mechanlcal Strengths 0f L 3 finished on an oxide basis: Product: I a P I The reducmg atmosphere immediately causes the ap SiO; from 6 to 8% pearance of a fairly large amount of a fibrous component. 2 fIom 1 to 2% For a same Blaine specific surface, for an aforesaid high- Al O from 18 to 20% alumina cement the results given in the following table Fe- O from 8 to 11% were obtained for a same cooling rate (from 1450 to CaO from to 34% 800 C. in 1 hour).

Gaseous medium, Compression strength in percent micro test-pieces Mineralogical composition, X-difiraction-Band intensity Ferrite CO 0; 6 hrs. 1 day 7 days CA CZAS C5A4Sf 2.66 A. 2.69 A. C285 C257 4. 5 0 33 78 298 9 82 117 52 1. 7 0 30 282 8 68 125 69 33 0 0 266 534 27 21 32 54 ll 13 0 4 131 330 536 49 15 27 106 63 ll The effect of the cooling rate is shown in the following table, which also indicates the mechanical strengths obtained on micro-test pieces of conventional industrial highalurnina cement.

0.65, that the crude is fused in a melting furnace in an oxidising atmosphere (about 3% 0 at a temperature in t a range of about 1400 C. to about 1500 (3., that Gaseous Compression strength medium in micro-test pieces Mineralogical composition, X -dttlraetion-Band intensity Ferrite Cooling rate (1) O0 0: 6 hrs. 1 day 7 days Ca C12A7 OcAS CQA-isf 2.66 Av 2.69 A. C256 C237 0 3. 8 55 192 540 68 42 0 4. O 142 458 622 123 65 0 4. 0 176 500 682 125 66 12 E 0 4. 3 556 632 134 76 5 22 Test piece of indusi high alumina cement 290 660 784 the molten clinker is then cooled slowly to a temperature The cooling rates being as follows:

Temperature observed following cooling tort 0 2 lggsd tco drop from 1,500 to 1,200 0., and 1 hr. to drop from 1,200 to of between 200and 800 C. at a cooling rate in the range The preceding figures and Table I below show that: of 250 to 1400 per hour, that said cooled clinker is th then crushed according to the mvemlon, to a Blame e CA and alummo ferrite contents lncrease when the 55 cooling rate decreases specific surface ($813) of 2500 to 3500 cm. /g., and preferably about 3000 cmF/g; with the slowest cooling, resistances at 4 h. and 6 h. are

A specific example of embodiment of the process substantially improved (about +50 to +60 bars) according to the invention is given hereinbelow. The cement according to the invention has? A starting mlxmre was used havm'g the followmg 60 good aging characteristics in thermal cycle (the thermal composmon: cycle is a test which reproduces in the laboratory the MIXTURE OF CRUDE 43% BAUXITE, 51% LIMESTONE heating cycle--i.c. cycle of heat evolved on setting- Determined which Occurs h n a large mass of concrete is used),

Bauxite Limestone crude which show, compared with the known industrial high- Composition otalumma 51 13. 2 0028 51 5.3 that the beginning of the rise in temperature Is very 42.60 0.10 18.40 close 2:.40 0.05 10.15 that heating (heat evolved on setting) is slightly less 0 0 0 P 0.05 0.02 0.03 70 that the maximum temperature reached (59 C.) is 0.03 0.01 0.02 k 1 b 6 C 16.85 43.80 31.80 mar e y Owen y As the second Table II hereinafter shows, mechanical test reveal the very important fact that, contrary to what occurs with industrial high-alumina cement, the rise in 7 temperature resulting from the thermal cycle has little Both components were crushed simultaneously so that not more than 5% of them would not pass through a 0.1 mm. mesh sieve.

effect on the strengths of CaO and SiO -rich high-alumina cement.

It is seen that G and SiO -rich high alumina cements enable mixtures to be formed quickly.

I.RESULTS OBTAINED WITH THE FOLLOWING CASTINGS, SLOWING DOWN THE COOLING RATE Compression strength, microconcret (W/C=0.40 bars) Ferrite Casting system CA CizAr CQAtSf CzAS C285 C257 2.66 A. 2.69 A. 4 hrs. 6 hrs. 1 day Casting ingot moulds, air-cooling. 36 11 18 10 8 74 67 70 195 555 Casting in crucible (=10 cm, height 25 cm.) insulated with insulating refractory concrete.- 1.Ea 48 20 26 ll 95 50 60 185 560 i ii iris riitiiih tig rh ifiiiei i ef p eir iieii at 64 11 24 17 15 1a 103 54 120 255 540 about 800 C I.MEC A TESTS 15 The refractory characteristics were studied, and are Percent dmpsin resistances summarized hereinbelow, by pyroscopic resistances and may 7 days 28 days giistance to ftwlilstmg (durmg helainlig at 1000 c) signation o t e cement: e ting point in 12 a 4 CaO and SiO -rich-high alumina cement, Industrial high-alumlnacement---. 44 42 46 20 Ja uary 1970 melt 1270 Industrial alumina cement sampled on:

From said tests it appears that resistance continues to November 12 1969 1280 increase rapidly after the thermal cycle, the strengths of December 1969 1290 the high-alumina cement according to the invention are slightly higher at 1 day (+40 bars) and substantially 25 P l of fusion of the f fl accordfng to 1116 higher at 7 and 28 days bars) invention 15 very close to that of 1ndustr1al alumma cement Underwater aging tests at 50 C. were also carried out t0 to determine the stability of the mechanical resistances TORSIONAL STRENGTH DURING HEATING AT 1,0000 CI and the kinetic of the development of hydrated aluminates. Test-bars made of microconcrete at W/C=0.40 are 30 'flg itfgi first aged for 28 days in moist air at 20 C., then im- Mortar used yp element 0,112 mersed in water at 50 C. Reckoning from said immer- Chamutte mortar C30 and SOmch high 30 sion, and at determined periods of time, the evoluation 51. at s u a m nta ordof strengths and the crystalline constitution are deter- 25 mi d. cement.

As to the crystalline constrution, the progressive disappearance of CAI-I and increase in the C AH content The C210 and SiO -rich cement is seen to have a slight is observed. advantage.

After 7 days under water at 50 C., it can be considered Finally differential deflection under 2 bars gave the that CAH has disappeared completely and that only 40 following results:

CQAH remains Testsearriedo twith h tte t SOGDAR t t f500k a This development is absolutely comparable to that u 0 a normally observed in industrial high-alumina cement. we mdefiecmn 1 2 5 Underwater aging at 70 C. was also observed. This Type of ment; test was carried out on 4 x 4 x 16 cm. prisms of micro- 2355:? i gggz gl sg g g 1 no 1 220 1 To 1 concrete at W/C=0.40. As soon as they are positioned, Industrial alumina ceme nt, 'c-.II 11140 11195 1; 250 1140 the test-bars are aged for 6 hours in steam at 70 C., immersed in water at These pflrtiwiafly The deflection under load of the binder studied is Severe test conditions have absolutely no beal'mg on practically equivalent to industrial alumina cement. ality, but permit minimum strengths to be determined. The tests carried out showed that the CaO and SiO Compared Wlth lndustl'lal hlgh'alumma cement, the rich cement according to the invention has a refractory strengths obtained with the product according to the power approximately the same as that of industrial mvemlon are: alumina cement. lower than 50 b ft a i d of 6 h Various known additives, notably lithium carbonate identical ft a period of 1 to 7 days. 5:: (from about 0.01% to 1% by weight of the cement) and calcium borate (from about 2% to 10% by weight Examination of the development of the crystallme conof the cement) have a favorable died on the strength stitution shows that, at 6 hours, the aluminates are comof cements according to the invention For instance pletely hydi'ated in cubic form which moreover cone 0.065% lithium carbonate added to the mixing water loglcaily to the weakest sirength observed enables the resistance at 20 C. to be doubled (from 70 to dustrial alumina cement behaves 1n the same manner 145 bars) after a Period of four hours and an increase under the same test conditions. of 30 bars at 6 hours The cement .according to the invention was tested as a From the standpoint of cost it should be noted that pure paste to discover its ability to form mixtures quickly. Cao and siorrich high alumi;la cements according to The tests gave the followmg results: the invention can be manufactured from SiO -rich Mixtumstested bauxites which are usually rejected for the manufacture of high-alumlna cements. 199mmt C80 Furthermore, a lower percentage of bauxite is used. rich $3. 53: These conditions of manufacture result in a cost apg ggg s Settingaspure paste proximately 30% lower compared with that of convenciflc surtri ce Percent Start, End, tional high'aluminacement- Pereent CPA 400 HTS 3,160 emJ/g. Hz min. min. What we claim;

20 32 21 40 1. A lime and silica-rich high-alumina cement consistgg 3* ing, in parts by weight, of about:

' s to 10% sio about 1 to 2% TiO 26 to A1203 14 to 16% Fe O or traces R20 45 to 48% CaO the moduli:

SiO /Al O +Fe O being in the range of about 0.18

Al O /CaO between about 0.55 and 0.65 and Al O /SiO between about 2.6 and 3.6 with a mineralogical composition containing CA, C S, C12A7 and ferrites.

2. A process for the manufacture of high-alumina cement according to claim 1, comprising the steps of mixing by crushing a silica-rich lbauxite and a limestone to form a crude having the following composition calculated on an oxide basis:

510;, from 6 to 8% TiO; from 1 to 2% A50 from 18 to 20% Fe O from 8 to 11% C210 from 30 to 34% MgO traces, with a ratio Al O /CaO from 0.55 to 0.65, fusing the crude in a melting furnace with an oxidizing atmosphere at about 3% 0 at a temperature in the range References Cited UNITED STATES PATENTS 3,298,843 1/1967 Asano 106l00 FOREIGN PATENTS 482,185 8/1929 Germany 106-104 OTHER REFERENCES Robson, T. D., High-Alumina Cements and Concretes, John Wiley & Sons, Inc., pp. 1927, 39 and 40 (1963).

JAMES E. POER, Primary Examiner W. T. SCOTT, Assistant Examiner US. Cl. X.R. 106-89,

IOP qK UNITED STATES ?ATE.NT OFFICE CERTIFICATE OF CORRECTION Patent No. ,7 15 Dated December 12, l972 Inventor(s) Reine Alege and Raymond Allegre It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 55, "ativate" should be --activate--; Column 2, line 41, "Al O CaO" should be -Al O /CaO--;

u l line 42, Al O /S:|.o should be Al O ./S:1.O Column 4,

line 23, "2.66 A. 2.69 A." should be -2.66 2 2.69 i

line 25, "33" (last figure) should be --39--; line 35, the placing of "Cooling rate" should be in the main heading on the line with "Gaseous medium"; line 35, "2.66 A. 2. 69 A." should be --2.66 2 2.69 3---; Column 5, line 33, "evoluation" should be -evolution-; line 36, "constrution" should be -constitution--'; Column 6, line 7, "2.66 A.. 2.69 A." should be --2.66 A 2.69 A"; line 33, "5 0 kg./m. should be --500 kg/m Signed and sealed this lZth day of June 1975.-

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents Webb STATEd e TENT @FFHCE QETEE EQATE F QGRIREE'HQ Patent No. 3,7os,815- Dated December 12, 1,972

Inventofls) Re ne Alegre and Raymond Allegro It iscertified that errorappears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

i Column 1, line 55, "ativate" should be activate-;

Column 2, line 41, "Al O CaO" should be --Al O /CaO-'-;

A El II -i llne -2, Al O /S1o should be Al O "/S1O Column 4,

line 23, "2.66 A. 2.69 An" should be --2Q66 23 269 ziv line 25, "33" (last figure) should be 39-; line .35, the placing of "Cooling rate should be in the main heading on, the line with "Gaseous medium"; line 35., 2.66 A0 2., 69 Au" should be -2.66 A 2.6-9 3-; Column 5, line 33, volu bi n" should be --evolution--; line 36, "oonstrution" should be --constitution- Column 6, line 7, "21.66 A.,. 2.569 A6? should be --2.66 23 2.69 A"; line 33, "5 o kg./m. should be --5o0 kg/m Signed and sealed this 12th day of June 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. 5 ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

